Automatic switch for use in telephone or like systems



Aug. 29, 1933. v w. G. PATTERSON El AL 2 AUTOMATIC SWITCH FOR USE IN TELEPHONE OR LIKE SYSTEMS Filed March 7, 1932 3 Sheets-Sheet 1 1 1 is m M 9,

I 1 l I 1-. I 1 t2 w-. noon 0' i Cc I M05 r 0 I P o o o o 1 n i I l l o o o o i I i l I I v EMT Inu'i n In?- Aug. 29, 1933- w. e. PATTERSON ET AL 1,924,454

AUTOMATIC SWITCH FOR USE IN TELEPHONE OR LIKE SYSTEMS Filed March 7, 1932 3 Sheets-Sheet 2 IfiFfi-TTEFE William 13. Pan-51 m BEE ET J. Each ET W Q m M -J w Aug. 29, 1933. w. G. PATTERSON ET AL 1,924,454

AUTOMATIC SWITCH FOR USE IN TELEPHONE OR LIKE SYSTEMS Filed March '7, 1952 3 Sheets-Sheet 3 TnuenlmFs Inlilliam G F'aflersun Ernest J. Gael-ET Patented Aug. 29, 1933 h umTEnqsrA @Ao'romrm swr r t f1;924 ,454 7 h 1 YHONEJQB LIKESWFEMS William owrge Patterson ma Ernest Jules Gacheti London, England; assiznqrs to' Siemens Brothers}: Company limited; London; Eng-'1 "land imam Maren- 7, 1932, seriaI'Nis'. '91142, I andin Great Britain'Mer'eh 17,1931

' r it cla ms enema-21.51)

This invention relates selecting/ switches for automatic telephone other selective systems' a'nd has mainly in View; an irnproved form of one-motion step by step selecting' switch although certain features of the in ve ntionv are applicable also to two motion switches.

According to the present invention the switch together with its control relay or relays is constructed as a single unit. The switch com prises a plate supporting a; s tep by step mechanism, a driying'magnet, and a control relay or relays. The magnet and-the relay or relays may be mounted on one side of the plateand the step by step mechanism on the other. flheplate may be of channel shape or may be a diecasting finclu ding fixing details, etc. The step by step mechanism includes a rackl a a r The. present invention is particularly appli-' cable to a switch in which the rack member earries wipers whichare adapted to enter a bare wire multipleb'ut the rack niembermay serve v so to produce a rotary movement: of wipers-over bank contacts.

For the control of ordinaryone-motion se-"J lecting switches a pairof relays ismrequired, one which when operated sets the Switch: in

motion and the other is"used as atest ielay to stop themotion of the switch on a desirefilout let being reached. In the ordinary subscribers preselector, for instance, i'hese relays are the line: i and test (or cut-off) relays-the linereiay start;

ing the switch in motion and the test relay stopping the motion or onincomi'ng calls disconnecte ing the line relay. t V v A feature vof'the switch of the present invention is that in a-one-motion switch the driving magnet itself acts as a line relay. When the switch is used as a searching switch it is arranged however that thema'gnet on energizing gives the rackmember a sing le' step whereupon a camsurface on the rack emirates on a memher which disconnects the starting circuit. and

' closes a local driving circuit. v Qbviously itmay spring In this arrangement m ma relay may,

be arranged that the magnet armature need, 7 not move to its full extentbefore .the localtir:

cuit is closed. An earlymake contact controlled by the armature maybe to assist "in meclosing of the local circuit.

It is arranged that switch self restoring in that the raclpis returned to-normal. by e.

be employed'as la retainingmagnet. It is then arranged that .on operating it inserts a retaining pawl into engagement witli the frack.x The r v usual retaining pawlisiurtherr'nore disengaged clejar of; the surface so that underits ownv 100 from the rack on operation of the n p messe ii t e sub quen "1 lease of thetestreIay until the rack; is at normal, A convenient way, of arranging forthis is to form the pawl asa spring member with}; twist v in it so that it may press' downwardly, and also be movable to one side. The mov ing rn a'y be i e t bro h? t t r ay; a mat re m hi intermediate member if necessary and' when "moved it may spring w at theside of themes] rack andbe lifted back :by'fmeansot a ramp to re-engage the rack as the normal posj tion is being reached. Ifhe driving {magnet "pawl; is

preferably normally out' of engagement with the a i rack and drops in after slightmoyernentofthe 7Q,

armature.

The withdrawal of th hoiaiiigheteiitmay I also becaused by a projection on the rack 'operating on theintermediatemember {say-a be11- crank) w h eri congestion or last contacts yare reached, in; which casewthe test relay need not be operated oncongestion occurring or theTlast.

, A iurfih r eat r pq fihe wi hi i t c- P 1 w t h rim to mar nes Whe t er k memb rrx ar i i h Wi rs. Thezm myb ar at its rear fend a block of insulating; material winch carriesn etal' strips that are ccmnected-tov h w p r "w th;t t i fqonne t dwth a e wiper e fiie ene wine lw y 1 5 0 tact; Spring-contactsare brought into contact \With the remaining strips when the test relay Q QIates;

In connection withthe local dr iving pircuitfl" 1 this must Jae-opened when thetest relay operates n i e; I 5 Wh l h ac u n a qin mal. g To produce this sequence of operations we may provide a spring with a twist in it; Nor-, I

1 r he r n marrie w er m t m e moved; side nwaysby a cam surface-en therack to en a e a-contact in; the local driving circuit I the SWitChfEj-tfiltfi}: When the 'tes trelay es. t e s n t l t d. y n x ee 1- h armature ofthe .relayciear of the contact-and tension it 'moyes sideways ;pnto; the .topQot the U can-1 'suriece thus preventingfanther closure oi t l d i nw wi -i Qui t of: e nk a normati e S n fof e rn ur c f ima pr v si I. e e n f We ls rin $9 i s na e WQQPQ: R me i i ar e ie-e be we r Video isi und rne th (and sm d? t R Pe- -F t ne -re er e .ee i 'wfi wn tact plate 9 5 im xtent o: me rpi os,

. erating on a pin attached to the spring to lift thespring from afixed contact. It may be pro-' vided that the fixed contact is only touched by the second spring when the rack member has left normal. I I

The switch when used as asubscriber s line switch may be provided with off normal contacts which when operated apply a busy condition" to} the subscribers line at the final switching stage.

The accompanying drawings illustratedby way" of example the features of thepresent invention applied to a switch employing a longitudinal rack member for operating the wipers, the electromagnets being secured to one side of a common mounting plate whilst therack member is mounted on the other side of the plate the armature of the electromagnets passing through the plate.

In the drawings Fig. 1 illustrates a circuit arrangement employing a switch according to the present invention. I a

side, plan" and end views respectively of the general mechanical arrangement'pf the switch,

whereas Figs. 5 and 6 give enlarged side and planviews respectively of the stepping mecha nism and the retaining pawl arrangements and several other detailsof the-switch; Thecircuit arrangement shown in Fig. l 'will first be described as this will enable the mechan ical arrangements subsequently described in con nection with the other figures to be more clearly,understood;

In Figlflthe portion markedLS is the -li'ne switch 'comprising wipers' W+, W,' WPand WM, the steppingmagnet M0, the multiplefield LSB, and testing relay T, The wipersnormah ly standout of the bank.

' away from each other untilthe wipercarri'age is restored to normal. 7 The contactsMCZ also have a peculiar operation, in that they remain in the normal position "shown until"the test relay T operates'whereupon they operate and change 1 over and remain-operated until the test relay is released whereupon the three "contacts are ten tirely-disconnected from each other until the wip'er carriage is returned to normal where they" 1 are again restored to their normal position as i The test relay T has three contactsjtl and t2 The contacts M03 openwhen the wiper shaft takes its first operating step. and 'the contacts M04 are operated directly on the energization of the electromagnet.

being. of the-change over type normally making with baclecontacts but making with the wipers W+ and W when operated, whereas contact t3 is of the xordinarymake type connecting up the diate lines, jumper wires.

circuitof thewiper WM when operated: v

The portionCC, of Fig. 1 -represents a cross connection field' interposed between the line representing terminal blocks and the-interme- V t V The 'subscribers line L'isconnected to the terminal block associated with the final selectors FS. Associated with each subscrihers line is'a'meter M, the connections to which are designated MW, and MR;

negative, and the private'or test "wire P;

battery and earth.

Figs. 2, 3.and 4 illustrate ergizing circuit over the subscribers line, but I after the first step of the wiper shaft and the operation of the contacts; MCl the magnet derives its stepping INT.

impulses from the interrupter contacts t2 and M01, stepping magnet M0 .to

Almost simultaneously with the energization of magnet M0 contacts M04 close and apply Considering the circuit in detail, when the,

. v 'positive wire, subscribers loop, negative wire earth to the magnet whereby it is held energized independentof the subscribers loop. The energization of magnet MC causes a pawlto operate andadvance the. wiper shaft by one step. Onthe advance of the wiper shaft contacts M01 change over and contacts M03 break. Contacts 1 M01 disconnect the original energizing circuit of the magnet MC, and apply thereto an interrupted earth from the interrupt-V er INT. The'wiper' shaft is 'thus'advanced step by step, the'wiper WP'being brought'into successive connection with theicontacts of test or 7 private wire leading-to the succeeding switching stage.-

The contacts M03 on opening disconnect the test potential from thefinalselector andthus render the calling line busy" to incoming calls. A'free outlet to a succeeding switching stage is "characterized by a battery; on the test wire and when the' Wiper WP [meets a free outlet the test relay T operates from earth contacts ing stage; a t I 2 connect the meter to'the wiper Contacts t3 WM over the wire MW in preparationfor the operation of the meter.

On the [operationfof relay T the contacts M01 are entirely disconnected fromeach other.

thus fop ening any" possible circuit of f magnet MC. Likewise the contacts MCZare changed bver, the bottom high resistance coil (II) of relay T thus being, disconnected and an'earth applied direct through the upper low resistance coil to the wiper-WP. This latter earth renders the outlet to the succeeding switching stage nonselectable to other searching line "switches,

whereas relay T is he ld to" the battery'on wiper.

to be disengaged therefrom and a temporary detent is inserted which holds the shaft whilst the switchis engaged, the-normal detent being rendered immune from any possible re'-' engage-. ment with'the teeth ofgjthe wiper shaft until it V t the wipers have been returned to normal.- switches and the final selectors FS, the circles The call to the wanted-subscriberjmay now proceed in well knownimanner, and when the wanted subscriber replies 'aba'ttery' is applied to the wiperWM, over contacts t3',wire MW, meter M wire MR/to earth. The meter operates and registers'the callagainst the callingsubscriber.

When the calling subscriber replaces his 're- ,ceiver at the termination of thej conversa'tion "the battery on the wiper WP is removed andl5 p 7 reggae; relay T releases. 3n the releas e of relay '1' the no circuit for relay T during the homing of to their normal positions, as shown the switch. V

When the wiper shaft reaches its normal position the contactSMCl, MC2, M03 are returned If the switch is unable to'find a free outlet to the succeeding switching stage, the switch wipers are advanced to their" ultimate positions and contacts M01 which in the case of finding a tree line were operated by the relay Tare now operated mechanically and thenormal detent holding the wiper shaft is mechanically tripped out and the wiper shaft returned to its normal position. If no special: provision is made to prevent the wiper arm from again 'being advanced, it continues to pass in and out of the bank until a free outlet is found.

When the subscribers line is seized from the final selector F-S a battery is applied to the wire P which battery passes over contacts M03, coils (I) and (II) of relay T, contacts MC2, to earth.

Relay T operates and at "contacts t1 and t2,

disconnects the circuit of magnet MC and prevents the switchfrom being operated. Arrangemerits are provided to prevent the operation "of relay T in this case effecting contacts MCI and Turning to Figs. '2 to 6, the components "of the switchers mounted on a longitudinal stampedorcast metal frame 1 provided at either side with turned over edges, the edges continuing beyond one of the frame to form fingers.

2 and '3 by which the switchis' supported in position on. the rack carrying the multiple banks. Electromagnets 4 and 5 provided with cores '6 and '7 and yokes 9 and 8 respectively are securedto the frame 1 by screws passing through the frame and engaging the yokes'8 and 9 or vice versa, as shown at 10. I v

On the top of the frame adjacent t fingers 2 and 3 is a terminal block 11 adapted to'enigage'a jack on the supporting frame to provide the electrical connectionsto the switch.

The wiper carrying shaft 14 is supported by a U-shaped metal piece 12 secured to the frame l by screws 13. The shaft comprisesv alongi}. tudinal T-shaped member, the edgeof, the trunk of the. T beingfprovided with teeth 'toform a rack. y t

-'I'he cross arm of the wiper shaft 14 lies b etween'theparallel limbs of the U-shaped piece 12, the ends of. the limbs being slotted and grooved to partially embrace'the crossfarm but v V p magnet .41is-1providedwith a bell crank-armature I 40, pivotinground "a. pin'h'eld in a bracket ernb'racingth'e yoke 9 in known mannenflThe allowing longitudinal movement thereof.

The shaft is shown carrying two sets of wipers 15 and 16 each set comprising two wipers. separated by insulating material, the :insulating material being riveted or otherwise secured to a limb of a .bifurcatedpbracket 17 whichin turn 7 is secured to the wipershaft in any. suitable manner. I

one at either side thereof. A pivot pin 23 passesthrough the brackets 22 and is'held in positionbrackets 34 secured to the 'frame' 1. I

Abracket 35 forming part: of piece 12 is bent up" at "rightangles to the base portion thereof being attached to spring.

'33 to contacts MC4Z h, r Continuing with thefdescription, the electro- "left.

tached tothe-yoke8 by" screws 26 and 2'7. A

by a claw 24 secured" to fair etatpiece25 at coiled sprihg 28 no" 'allymaintains thejarma Alsoto the same end' of the'arm 29 is secured a pin 32 adapatedto normallymaintalnbpeh the. contact springs 33 which are supported by and is bifurcated at its end, the fingers being so bent that one 35a is'disposed infront of and overthe pawl 31, whilst the other lingo-r1351) is beneath the pawl. These two fingers serve to guide the pawl in its operative and retractive movements.

'The normal retaining pawl 36'is riveted to a leaf spring 3'7 secured to a bracket 38,-which bracket is attached by screw 39 to a further 7' turned up portion of piece 12. 'The leaf spring;

37 is twisted so thatits twoparts are substan- I tiallyat righ-tangles to each other,thus allowing movement in two directions,gthe* pawl 36 the horizontal part of the Theoperation ofthe partsoi" the's witch just described isasfollows; I

When the electromagnet 5';is energized the armature is rotated about the pivot pin 23 and moves to the left carrying withit the arm and is thereby guided" into engagement. with the first-toothpftherarik on the wiper shaft.

During the continued forward movement Of fth e' pawl the wiper shaft is pushed forward (to the left) one 'step against the tension of spring 19.

The normal retaining pawl 36 rides over teeth in the rack as the shaft moves forward and when each/complete step is taken engages a next tooth in therack and- 'pre'vents' the. return of the wiper shaft. When the arm 29ymoves tothe. left the pin 32' mevesjwah it and allows the contact springs 33 to rn'akeconta'ct. When 29. spring 30;and pawl'Bl. The pawl rides below the'upper finger 35a of the bracket 35 that the'electrornagnet 15 corresponds to stepping magnet M in FigJL and contact springs.

armature" is provi'ded with *an adjusting screw- 42, being secured thereto byscrewsgthe' arm being 'L-shaped. sov as to pass round and "over theftop of the wiper shaft. The free end of 4:1" opposite; the core '7." Continuing parallel with the vertical'part of the'armature is an-arni the arm is turned round at rightangles and Iin- I clined frorh the horizontal. A temporary reg.

' taining, leaf spring pawl 43 is screwed to this inclined part of the arm 411and is maintained arrangement of described. V

ttached beneath the end of the wipertcarrying shaft 14, at theopposite end to that carrying the wipers 15 and 16, is a block 47 of insulating material and stretched along the length of and over the bottom of this blockare four stout feeder wires 48, the wires being terminated at-two little blocks 49 and 50 attached to or integral with the block 47. The wires are taken through holes in the blocks,over the top of the blocks, and then through further holes. These the frame 1. .60 are first moved laterally, the 'spring '59 passfeeder wires are provided for the electrical 0on nections to the pairs. of wipers 15and 16, further wires being connected to the wires and led alongone side of the cross arm of the T-shaped wiper shaft, the wires beingcovered by a channel 51, which channel is-shownV-shaped.

Situated beneath each one of three of the feeder wires 48isa pair, of contact springs 52 and '71, the upper spring of each pair being provided with a lip 53. Each pair of contact .springs is adapted to normally be' in electrical. connection but whenoperated the upper spring, with the lip rises' breaking connection with its bottom spring 71 and the ,lip. 53 makes connection with its appropriate feeder. wire 48.-

A fourth contact spring 54 is prQVided which permanently lmakes contact .with the fourth feeder wire. The contact springs are secured into an insulating block .55 attached to the frame 1., v I. I At one side. of the insulating block 4'7 is a bridge 56 extending along the length of the block.

c A bracket" 57 secured to the frame 1 carries an insulating block. 53 which supports contact springs 59 and 60.1 Acontact 77 for making a through connection also being supported. These contact springs are bent at righteangles along their lengthso that" theyare; allowed movement in the two directions, that is, sideways andupwards. The, contact springs are secured .together at their free ends by an i'nsulatingpiece 69, the insulating piece beingp'ro'vided with a rnent being adapted to make contact' with one or other of the fixedcontactsfil or 62. The lower. spring makes connection wholly throughout its lateral movement with fixed co'ntact 63. The fixed contacts 61, .62 and 63 are supported in an insulating block 64 secured to In operation the springs '59 and ing from contact 61 to contact 62, after, which lateral movement the springs are moved upward to entirely break contact with the-fixed contacts. I I

Referring now to the horizontal arm'of the *bell crank armature 40, this arm is provided with an extension arm '65, bent upwards at rightthe contact springs will bev bridge on the block 47 moves forward and the projection '70 rides on to the top of the bridge piece'56 and as a consequence the insu When the wipers meet afree' outlet to the arm 41 moves, to the left. 1 q vWhen the extension arm 65 moves, the, consulating block 66 bridging the two limbs.v .The block 66. is adapted to be disposed over and T press on to the upper contactsprings of the pairs of springs 52 and thereby normallymaina tainthe pairs of springs in contact. Also at the point where the. extension arm 65 is bent upwardly at right angles is secured afurther insulating block 67 carrying a small contact, piece 68. V I

. The contact piece 68 isdisposed below butnot normally in contact oraligninentwith a metal pin 72 inelectrical contact with springfif). The inner edge of the contact piece 68 is turned up slightly so that when in electrical connection with pin '72, the pin is prevented from sliding off.

To the extremity of the frame l'is attache'd apair of contact springs '74 normally maintainedin contact by the pressure of the end of the wiper shaft 14.

From the cross arm of the T-s'haped Wiper" shaft just behind the rack in the trunk thereof, projects a pin 75. This pin represent's the ultimate operative position of the switchandwhen' such a position is reached" the pin '75 registers with one arm of the bell crank lever 45. v

, The operation of the items just described will. now be explained.v

t will be remembered that the wipershaft 105 has previously been described as being stepped by the magnet '5, the-wipers 15 and 15 thereby being stepped into the bank, the magnet 5-cor responding to stepping magnet MC and the contact springs 33 to contacts M04 in Fig.1 The magnet 4' corresponds, to test'relay T, Fig. 1,'the contact spring 59 and fixed contacts 61 and 62' to contacts MCl, the contact spring GOQfixed contact 63, pin 72, and contact piece 68 correspondto contacts M02, contact springs 58 to contacts t1, t2 and t3, spring54 to the connection betweenthe "wire P and the wiper WP, and

ftheccntact springs 74 to contacts MC3.

.When. thewiper shaft takes its first step, the

lating piece, 69 and the contact springs 59 and 60 are pushed outwardly.v The contact spring 59 moves fromffixedcontactfil to contact 62, bridgingthe two contacts during a'portion of its travel. The spring 60 slides over the sur-- face of fixed contact 63, but, does not break connec'tionjtherewith, and the pin72 attached to spring 60 moves over the top of, and in alignment with contact piece 68, but doesnot make contact therewith. j

1 Also on the firststep of the wiper shaft the two contact springs 'l t'break from each other. It will be remembered that. when the relay T Fig. 7- operates the contacts MCI areljentirely disconnected from each other whilst the contacts MC2 are changed over.

succeeding switching stagethe magnets is energized and the armature i0 attracted.

The extension arm 65 moves upward v whilst V tact springs 52 are released and allowed toincve upward, breaking connection with their lower contact springs '71 and making connection'withr the feeder wires 48, which. as will be remembered in connection with l ig". '1-"disconnects the original operating circuit. of relay M and Iconnects up the speaking wires to theiwipers f Also the contact piece 68 -moves upwards carrying with it the pin "72 and contactsprings; 59 and 60. The springs 59 and break con- Turning now to the arm42, whenthisirnovesv to the left, the temporary retaining pawl 43 is inserted into a tooth of the rack on. the wiper shaft almost simultaneously with which operation the arm-strikes oneiam"of the bell crank lever 45. The latter rotates and encounters the spring 3'7 carrying the normal retain- I Letters Patent is 1;

ing pawl36 and pushes the pawl'out of engagement with the rack. By reason of; the tension in the horizontal part ofthe spring 37 the Y pawl 36 slips down to the side of the rack, the

wiper shaft being prevented from restoring by the temporary retaining pawl 43.

The switch remains in this position until magnet 4 is released at the termination of the mal under the tension of spring 19.

When the arm moves downwards the contact piece 63 breaks connection with the pin '72 and consequently with the spring 60.

When the armature 40, restores the contact piece 68 moves downwardly, and by reason of the lip on the contact piece moving out of the 'way ofthe pin 72' the springs 59 and 60 move sideways and the projection on the block 69 clips over on to the upper surface of the bridge 56, thereby preventing the downward restoration of the springs whilst the wiper shaft is off normal.

The contact springs 59 and 60 are thus held in their upward position during the restoration of the wiper shaft'by reason of the projection '70. bearing on the upper surface of bridge 56,

but when the switch reaches normal the projection slides off the bridge, allowing the-springs to restore. i

Further at the side of the rack to whichthe retaining'pawl 36 is pushed by thebell crank lever 45 is a cam 'lfi corresponding in position to the normal position of the wiper arm. 'Thus when the wiper shaft restores the cam slides under the pawl 36 and pushes it upwards,,the

pawl thereupon being forced into a tooth by the lateral tension of springs 37. a Y 7 If the switch is stepped ,to its ultimate posi tion without magnet 4 energizing the pin'75 strikes one arm' of the bell crank lever 45 causing this to rotate and force the retaining pawl i out of engagement with the rack on wiper shaft 14. f Also a ramp on the bridge piece 56 is so disposed as to engage pin 70 when the wiper shaft is stepped from its penultimate to its ulti mate position. The effect of the ramp is .to

.. raise springs 59 and 60 out of engagement with The 7 their respective, fixed contacts. .62 and 63,

thus simulating the operation of-armature .40,

shaft reaches its normal positionlthe pawltfi is again guided, into. engagementwith the rac by cam' 76, asbefore described.

. It is to be understood For example, an

The wiper shaft thereupon restores to normal under the tension of spring l9, and when the.

a that many modifications may be made to the details comprising the switch without departing from thespirit of ,the'

present invention. '1

arcuate bani; may be emplayed, the wipers beingpivoted so; as to rotate.

round thebank. The 'wiper shaft will'engage a slot inthe wipers so that although ;the shaft moves'along the same straight line the wipers will bepnshed so a sto rotate through .the'neces saryara. i l a .FurtherQ-the feeder wires 43 may be replaced by fiat metal strips'mouldedintofthe block 47; and the vlittle b'locks 49. and -.50 dispensed with,

ing. wires thereto. What weclaim as new and desire to secure by 1. An electromagnetic step-by-step switch having a commonfraine, a wiper carrying element mounted on said frame, a pair. of magnets mounted on said frame, meansoperated by one magnet for operating the wiper element'step by step," means for holding the element in advanced position at certain times, and. means controlled by the other magnet for holding the element in, advanced positionat other times.

2. A step-by-step switch having'awiper carrying element, means" for advancing, the element a mechanical detent for holding the elethe strips 1 being provided withmeans for solder-;

ment in advanced position only during its adwvancement, another detent, and an el'ectromag net for operating, said other detent toengage the element simultaneously'with' or just prior to the disengagement of the mechanical detent.

]3. A step-by-step switch having a wiper carrying element, means for advancing the element, a mechanical detent normally holding the element in advanced position, a temporary detent, an electromagnet, and means operated by the magnet for removing the mechanical detent and causing the temporay detent to engage and hold the element in advanced position. 7

i 4. A step-by-step switch havinga Wiper carrying element, means for advancing the element a mechanical detent normally holding the element in advanced position, a. temporary detent, an electromagnet, and means operated by the magnet for removing the mechanicaldetent and causing the temporary detent to engage and. hold the element in advanced position, said mechanical detent carried on one end of a leaf spring twisted at right angles to itself at a point along its length so that the end carrying the detent is movable in two places;

5. A step-by-step switch having a mechanical detent normally-holding the elea wiper carrying element, means for advancing the element,

ment in advanced position, a temporary detent,

an electromagnet, means operated by the magnet for removing the mechanical detent and causing the temporary detent to engage and hold the element in advanced position, and

means controlled by the element when moved to element to causethe wiper to pass overcontacts;

circuit controlling contact springs, an electromagnet having means for controlling the switch magnet.

Operation, said springs controlled both by the position of the element and by the magnet.

In a step-by-step switch having a wiper carrying element and means for advancing the same, a set oi springs having movement in two -planes, a magnet, means on the element for moving the springs in one plane and means controlled by the'magnet for the other plane.

8. In an electromagnetic step-by-step switch, wipers, a wiper carrying element,'an electroimagnet forpartially controlling the operation of" the element; said elementand magnet mounted j on a common frame, contact springs controlling the connection of the wipers to external circuits; said springs operated by said 9. An electromagnetic step-by-step switch having wipers, a magnet having means for movmoving the springs in ing said wiper S;:asubscribers line connected to thesswitch, a circuit'for energizing the magnet including the line, and means controlled by the initial energization of the magnet over the linethe magnet inmagnet from the loop and connecting it to the intermittent source; said magnet operated thereafter from said source until an idle trunk is found by the wipers," and means operated when such'idletrunk is found for disconnecting the magnet from-ithe intermittent source and maintaining the original circuit forthe magnet open until the" switch is released. 7

WILLIAM GEORGE PATTERSON;' ERNEST JULESGACHET. 

